This invention relates to a transit mixer, and more particularly to a contractible-extendable trailer transit mixer adapted to discharge forwardly of the truck.
The necessity for moving large quantities of building material such as concrete for long distances has resulted in various styled trucks designed to address particular requirements. These truck designs were of two basic types. First, and most popular, the mixer drum was mounted on the truck body thereby providing acceptable maneuverability of the vehicle. Second, the mixer drum was mounted on a trailer portion, which was then secured to the truck. This trailer configuration resulted in greater pay load capability due to better axel load characteristics but sacrificed maneuverability.
The previous forms of trailer transit mixers consisted of a trailer upon which a mixer drum was mounted, which held the pay load during transit, and U.S. Pat. No. 3,038,704 illustrates one such trailer unit. An engine or other drive mechanism was connected to the mixer drum to cause rotation and provide the desired mixing necessary for the concrete. The mixer drum was positioned on the trailer with the open end at either the front or rear with discharge chutes mounted at the open end to discharge concrete at the front or rear of the trailer depending upon the operational characteristics desired. In the configuration of U.S. Pat. No. 3,038,704, the drum was rotatably mounted to point forward on a trailer which was slidably engaged with the truck. However, this form had severely impaired turning capabilities when in the contracted configuration due to the contracted trailer portion extending along side the truck cab.
Other trailer type devices have been used with transit mixers to increase the payload carried by the mixer drum, such as those of U.S. Pat. Nos. 3,019,002 and 3,112,100, but the prior art trailer devices had certain limitations and undesirable characteristics.
Due to the highway regulations of the Federal Government and all states, there are severe restrictions on the size and loading of trucks and trailers that use public roads. In particular, various limitations exist on the weight per axle per unit length of truck allowable on public highway facilities. For example, the Federal highway regulations provide weight limitations of less than 80,000 lbs. for vehicles, regardless of the number of axles, of a length less than 50 feet 6 inches between the extreme spaced axles. With extreme axle spacing of 51 feet or longer, a total weight of 80,000 lbs. is allowable. Therefore, by simply making the transit mixer drum larger, thereby increasing the payload and weight but without increasing the length, the manufacturer and user may face violations of Federal or State Codes. However, by just making transit mixers longer, particular multiaxle trucks, manueverability problems exist at the job site. Also, in the longer transit mixer configurations insufficient drive wheel traction can occur when at the job site, thus reducing the ability of the trailer transit mixer to negotiate adverse terrain. There are still further State and Federal highway regulations that limit the magnitude of weight allowable on any single axle or on tandem axles.